As is known, "one-and-a-half breaker" substations serve to feed two separate outgoing feeders provided by cables from one or other of two incoming feeders provided by overhead lines or cables, using a configuration that requires only a small number of circuit breakers. This configuration is shown diagrammatically in FIG. 1, having two possible incoming feeders and two possible outgoing feeders.
Each of the two incoming feeders 1, 1' is powered via a polyphase link 2, or 2' (generally a three-phase link) which is connected to an incoming disconnector 3 or 3'. A circuit breaker 4 or 4' is located downstream from each incoming disconnector going away from the link 2 or 2' that terminates on said incoming disconnector, and serves in turn to feed cables 5 or 5' via respective so-called "intermediate" disconnectors 6 or 6'.
An additional circuit breaker 4" is connected between two disconnectors 7 and 7' referred to as "middle" disconnectors which are connected one to the fixed contacts and the other to the moving contacts of the interrupter chambers (not shown) of said circuit breaker for each of the power phases. It is the circuit breaker 4" that acts as the half breaker for the "one-and-a-half breaker" substation.
Each middle disconnector 7 or 7' is also connected to the cables of a respective one of the outgoing feeders 5 or 5' together with one of the intermediate disconnectors 6 or 6'.
Toroidal type current transformers 8 are mounted for measurement and management purposes on each incoming feeder 1, 1' upstream from the correspond incoming disconnector 3 or 3', and on each outgoing feeder 5, 5' downstream from each of the two disconnectors connected to a given outgoing feeder, i.e. its intermediate disconnector 6 or 6' and its middle disconnector 7 or 7'.
The subassemblies such as the circuit breakers, the disconnectors, and the current transformers that make up such substations are generally separate from one another and are interconnected as required by conductive links implemented in the form of air-insulated busbars. A substation of this kind is therefore of large dimensions and as a general rule gives only a limited picture of the overall circuit to which it corresponds.